Orion Nebula (Messier 42)

Orion Nebula – 16th Feb 2021

The Orion Nebula is probably the most popular target in Astro-Photography as it is both relatively bright and also easy to find.  Located in the sword of Orion, the nebula is the closest star forming region to Earth, at a distance of  just over 1,300 light years. It is 24 light years across, with a mass of about 2000 solar masses.  The nebula is illuminated by a group of 4 tightly packed stars known as The Trapezium. As these stars are quite bright, it makes it a challenge to photograph the faint details of the outer reaches of the nebula without over-exposing the core, so often astro-photographers will combine different exposure lengths together, effectively creating an HDR image.

The nebula is also surrounded by some relatively bright stars, most notably the star Hatysa at magnitude 2.75, which can be seen just to the right off the nebula. However this proximity is an accident of alignment, as Hatysa is actually 1000 light years more distant than the nebula.

The main nebula is surrounded by other smaller nebula such as De Mairan’s nebula (the small area below the main ‘shell’) and the Running Man nebula (the blue region to the left). The whole region is in fact one large nebula structure, but as parts of the nebula are obscured by darker clouds of gas and dust, this gives the impression of separate nebula.

Although the Orion Nebula is visible to the naked eye, it was not mentioned by the Greek Astronomers such as Hipparchus or Ptolomey, so was not identified until the early telescope observations by astronomers such as Galileo and Hodierna in the 17th century.  In the late 18th century, Messier first published his list of astronomical objects, which was primarily drawn up to avoid confusing these objects with comets – the Orion Nebula was a late inclusion at number 42. By this time the Orion Nebula was well known to astronomers, and there was little chance of confusion with a comet, so it is likely that Messier expanded his list by adding a few well know objects, probably to exceed the list of 42 objects previously compiled by the astronomer Lacaille in the late 17th century.

This image was photographed in two sessions about 1 week apart, each adding just over 1 hours worth of total integration time.  From the North of England, Orion is fairly low in the sky, so is difficult to photograph for a really extended session, however on both these occasions, the image time was cut short by clouds.  Two and a half hours is however plenty of time to extract a great deal of detail in the main nebulous areas, however even longer exposures (or imaging from a dark sky site) would be required to show the darker dust regions more clearly.    

Image Details

  • Date: 8th & 16th Feb 2021
  • Exposure Details: 47 x 200s, F6, ISO400
  • Total Integration Time: 2hr 37min
  • Camera: Canon EOS80D (unmodified)
  • Telescope: Altair Astro 72EDF at 432mm focal length.
  • Mount: Skywatcher HEQ5
  • Guide Scope: Altair Astro 60mm
  • Guide Camera: QHY5LII

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